1. Field of the Invention
In one of its aspects, the present invention relates to the hydrophobicizing of particles, particularly mineral particles that are hydrophilic and have surface hydroxyl groups, for example silica, silicates, clay, alumina, titanium dioxide and the like. The invention also extends, however, to treatment of non-mineral particles, for instance carbon black. In another of its aspects, the present invention also relates to the treated partices, per se. The treated particles are useful particularly, but not exclusively, as a filler in polymers, especially rubber. In another of its aspects, the present invention, also relates to a filled, particularly silica-filled, rubber masterbatch, and to a process for preparing it.
2. Description of the Prior Art
In recent years, there has developed a considerable interest in silica reinforced tires, particularly since the appearance in 1992 of the Groupe Michelin (G-M) patents (EP 05 01 227 A 1; AU-A-111 77 192) indicating that tires made with tread formulations incorporating silica enjoy some important performance advantages over those based on conventional carbon black filler. Improvements are claimed for this xe2x80x9cGreen Tirexe2x80x9d in the areas of (a) lower rolling resistance, (b) better traction on snow, and (c) lower noise generation, when compared with conventional tires filled with carbon black.
Rubber for tires is often supplied by a rubber producer to a tire manufacturer in the form of a masterbatch containing an elastomer, which is typically a hydrocarbon rubber, an oil extender and a filler. The conventional filler has been carbon black in the form of fine particles. These particles have hydrophobic surface characteristics and will therefore disperse relatively easily within the hydrophobic elastomer. In contrast, conventional silica has a relatively hydrophilic surface, and considerable difficulty has been encountered in dispersing conventional silica in the hydrophobic rubber elastomer.
In the past, efforts have been made to make masterbatches from elastomer dispersions and aqueous dispersions of silica pigment, such as those referred to and attempted by Burke, in U.S. Pat. No. 3,700,690. Burke attempted to overcome the previously known difficulties of incorporating fine particles of silica uniformly into a masterbatch. At the time of the Burke invention, there was no known elastomer-silica masterbatch offered in the commercial market. Similarly today, to the Applicant""s knowledge, there are no commercially available in situ produced elastomer-silica masterbatches in the market, despite the efforts of Burke (i.e., conventional elastomer-silica masterbatches are produced and available in the dry state).
It is an object of the present invention to obviate or mitigate at least one of the above-mentioned disadvantages of the prior art.
It is another object of the present invention to provide a novel, relatively hydrophobic particulate material.
It is yet another object of the present invention to provide a novel process for treating particulate material to render it relatively hydrophobic.
It is yet another object of the present invention to provide a novel masterbatch composition comprising an elastomer and a relatively hydrophobic particulate material.
It is yet another object of the present invention to provide a novel process for producing a masterbatch composition comprising an elastomer and a relatively hydrophobic particulate material.
Accordingly, in one of its aspects, the present invention provides a process for treating particles, particularly mineral particles, to render them hydrophobic, the process comprising the steps of:
(a) contacting the particles with a compound of Formula I: 
xe2x80x83or an acid addition or quaternary ammonium salt thereof, in which:
at least one of R1, R2 and R3, preferably two of R1, R2 and R3 and most preferably R1, R2 and R3 are hydroxyl or hydrolysable groups;
R4 is a divalent group that is resistant to hydrolysis at the Sixe2x80x94R4 bond;
R5 is selected from the group comprising: hydrogen; C1-40 alkyl; a C2-40 mono-, di- or tri-unsaturated alkenyl group; a C6-C40 aryl group; a group of the formula: 
xe2x80x83in which x is an integer from 2 to 10, R13 and R14, which may be the same or different, are each hydrogen; C1-18 alkyl; C2-18 mono-, di- or tri-unsaturated alkenyl; phenyl; a group of formula: 
xe2x80x83wherein b is an integer from 1 to 10; a group of formula: 
xe2x80x83wherein c is an integer from 1 to 10 and R22 and R23 which may be the same or different, are each hydrogen, C1-10 alkyl group or C2-10 alkenyl group, provided that there is no double bond in the position alpha to the nitrogen atom; a group of formula:
xe2x80x94[(CH2)rNH]dxe2x80x94H
xe2x80x83wherein r is an integer from 1 to 6 and d is an integer from 1 to 4;
R6 may be any of the groups defined for R5, or R5 and R6 may together form a divalent group of formula: 
xe2x80x83in which A is selected from the group comprising xe2x80x94CHR or xe2x80x94NR group in which R is hydrogen or a C1-40 alkyl or C2-40 alkenyl group, a C6-C40 aryl group, an oxygen atom and a sulfur atom, and t and v are each independently 1, 2, 3 or 4; provided that the sum of t and v does not exceed 6, and is preferably 4; and
(b) contacting the particles with a compound of the Formula II: 
xe2x80x83in which:
R15, R16 and R17 have the same definitions as R1, R2 and R3; and
R12 is selected from the group comprising a C8-40 alkyl group or a C8-40 mono-, di- or tri-unsaturated alkenyl group, either of which can be interrupted by one or more aryl groups, preferably phenyl groups; a group of formula: 
xe2x80x83or an acid addition or quaternary ammonium salt thereof in which R18 is a divalent group resistant to hydrolysis at the Sixe2x80x94R18 bond, R19 is selected from the group comprising hydrogen, a C1-40 alkyl group, a C2-40 mono-, di- or tri-unsaturated alkenyl group, a substituted aromatic group, for example the phenylene group xe2x80x94(C6H4)xe2x80x94, the biphenylene group xe2x80x94(C6H4)xe2x80x94(C6H4)xe2x80x94, the xe2x80x94(C6H4)xe2x80x94Oxe2x80x94(C6H4)xe2x80x94 group or the naphthylene group, xe2x80x94(C10H6)xe2x80x94, the aromatic group being unsubstitued or substituted by a C1-20 alkyl or C2-20 mono-, di- or tri-unsaturated alkenyl group; and R20 may be any of the groups defined for R19, with the provisos that R19 and R20 do not have a tertiary carbon atom adjacent to the nitrogen atom and that at least one of R19 and R20 has a carbon chain at least 8 carbon atoms in length uninterrupted by any heteroatoms.
Preferably, R18 is a C1-C40 saturated or unsaturated group (e.g., alkenyl, aryl, cycloalkyl and the like).
In the present process, Steps (a) and (b) may be conducted concurrently or sequentially. If Steps (a) and (b) are conducted sequentially, it is preferred to conduct Step (a) followed by Step (b).
As will be apparent to those of skill in the art, there are instances where Formulae I and II may be the same compoundxe2x80x94e.g., when R5=R19=a C8-40 alkyl group or R5=R19=a C8-40 mono-, di- or tri-unsaturated alkenyl group. Thus, in such cases where Formulae I and II are the same compound, it will be clearly understood that the present process intentionally embodies a single step process (i.e., where the compound of Formulae I and II is added in a single step) and a multi-step process (i.e., where the compound of Formulae I and II is added proportionally in two or more steps).
In another of its aspects, the present invention provides a treated particulate material comprising particles having bound thereto an aminohydrocarbonsiloxane (e.g., an amino(alkyl)siloxane) moietyxe2x80x94i.e., a hydrocarbon moiety comprising both silicon and nitrogen.
Preferably, the aminohydrocarbonsilane moiety has the formula 
in which:
Ra, Rb and Rc are the same or different and each is selected from xe2x80x94Oxe2x80x94 and xe2x80x94CpH2pxe2x80x94, optionally substituted by one or more oxygen atoms and wherein p is an integer of from 1 to 10; and
R12 is a C8-40 alkyl group; a C8-40 mono-, di- or tri-unsaturated alkenyl group; a group of formula 
xe2x80x83or an acid addition or quaternary ammonium salt thereof in which R4 is a divalent group resistant to hydrolysis at the Sixe2x80x94R4 bond, R5 is hydrogen, C1-40 alkyl, C2-40 mono-, di- or tri-unsaturated alkenyl; a group of formula
xe2x80x94ArCwH2w+1
xe2x80x83in which Ar represents a divalent aromatic group and w is an integer from 1 to 20, and R6 may be any of the groups defined for R5, with the proviso that at least one of R5 and R6 must have an uninterrupted carbon chain at least 8 carbon atoms in length.
In yet another of its aspects, the present invention provides a particulate material comprising particles having: (i) bound thereto an aminohydrocarbonsiloxane (e.g., an amino(alkyl)siloxane) moiety (i.e., a hydrocarbon moiety comprising both silicon and nitrogen), and (ii) a contact angle of at least about 100xc2x0. Preferably, the aminohydrocarbonsilane moiety has the formula set out hereinabove. Preferably, the particles have a contact angle of at least about 110xc2x0, more preferably in the range of from about 115xc2x0 to about 160xc2x0, even more preferably in the range of from about 120xc2x0 to about 150xc2x0, most preferably in the range of from about 120xc2x0 to about 140xc2x0. In contrast, the contact angle of silica particles which are not treated in accordance with the present process is typically 75xc2x0.
The contact angle of the particles with water may be readily determined according to the following procedure:
(i) double-sided tape is attached to a probe (e.g., a stirrup) and coated with the particulate material by immersing the tape in a sample of the particulate material;
(ii) excess powder is removed by gentle tapping and large powder clusters are removed by careful wiping;
(iii) the probe coated with particulate material is immersed into distilled water using a conventional contact angle analyzer (e.g., a Cahn Dynamic Contact Angle Analyzer) at a rate of 100 microns per second.
This procedure results in determination of the advancing contact angle of the particles.
In yet another of its aspects, the present invention provides a particulate material produced by contacting the particles with a compound of Formula I: 
or an acid addition or quaternary ammonium salt thereof, in which:
at least one of R1, R2 and R3, preferably two of R1, R2 and R3 and most preferably R1, R2 and R3 are hydroxyl or hydrolysable groups;
R4 is a divalent group that is resistant to hydrolysis at the Sixe2x80x94R4 bond;
R5 is selected from the group comprising: hydrogen; a C1-40 alkyl; a C2-40 mono-, di- or tri-unsaturated alkenyl group; a C6-C40 aryl group; a group of the formula: 
xe2x80x83in which x is an integer from 2 to 10, R13 and R14, which may be the same or different, are each hydrogen; C1-18 alkyl; C2-18 mono-, di- or tri-unsaturated alkenyl; phenyl; a group of formula: 
xe2x80x83wherein b is an integer from 1 to 10; a group of formula: 
xe2x80x83wherein c is an integer from 1 to 10 and R22 and R23 which may be the same or different, are each hydrogen, C1-10 alkyl group or C2-10 alkenyl group, provided that there is no double bond in the position alpha to the nitrogen atom; a group of formula:
xe2x80x94[(CH2)rNH]dxe2x80x94H
xe2x80x83wherein r is an integer from 1 to 6 and d is an integer from 1 to 4;
R6 may be any of the groups defined for R5, or R5 and R6 may together form a divalent group of formula: 
xe2x80x83in which A is selected from the group comprising xe2x80x94CHR or xe2x80x94NR group in which R is hydrogen or a C1-40 alkyl or C2-40 alkenyl group, a C6-C40 aryl group, an oxygen atom and a sulfur atom, and t and v are each independently 1, 2, 3 or 4; provided that the sum of t and v does not exceed 6, and is preferably 4;
and a compound of the Formula II: 
in which:
R15, R16 and R17 have the same definitions as R1, R2 and R3; and
R12 is selected from the group comprising a C8-40 alkyl group or a C8-40 mono-, di- or tri-unsaturated alkenyl group, either of which can be interrupted by one or more aryl groups, preferably phenyl groups; a group of formula: 
xe2x80x83or an acid addition or quaternary ammonium salt thereof in which R18 is a divalent group resistant to hydrolysis at the Sixe2x80x94R18 bond, R19 is selected from the group comprising hydrogen, a C1-40 alkyl group, a C2-40 mono-, di- or tri-unsaturated alkenyl group, a substituted aromatic group, for example the phenylene group xe2x80x94(C6H4)xe2x80x94, the biphenylene group xe2x80x94(C6H4)xe2x80x94(C6H4)xe2x80x94, the xe2x80x94(C6H4)xe2x80x94Oxe2x80x94(C6H4)xe2x80x94 group or the naphthylene group, xe2x80x94(C10H6)xe2x80x94, the aromatic group being unsubstitued or substituted by a C1-20 alkyl or C2-20 mono-, di- or tri-unsaturated alkenyl group; and R20 may be any of the groups defined for R19, with the provisos that R19 and R20 do not have a tertiary carbon atom adjacent to the nitrogen atom and that at least one of R19 and R20 has a carbon chain at least 8 carbon atoms in length uninterrupted by any heteroatoms.
Preferably, the present process of treating a particulate material is carried out in an aqueous solution, dispersion or slurry, so that the product of the process is an aqueous dispersion or slurry of hydrophobicized mineral particles.
In one preferred embodiment, the dispersion or slurry resulting from the present process, and containing the treated particles (preferably mineral particles such as silica), is then mixed with a hydrocarbon solution of an elastomer, and then dried to form a silica-filled rubber masterbatch. Owing to the hydrophobicized nature of the silica filler, it is well dispersed in the elastomer. This preferred embodiment results in the in situ production of a masterbatch composition comprising the elastomer and the treated particles. By xe2x80x9cin situ productionxe2x80x9d is meant that treated particles are incorporated into a masterbatch composition without being isolated (i.e., separated from the dispersion or slurry, and subsequently dried). This preferred embodiment is believed to be the first in situ production of a masterbatch composition comprising an elastomer and a treated particulate material such as silica.
Alternatively, the treated particulate material may be separated from the dispersion or slurry, and subsequently dried for later use.